The invention relates to the technical field of new materials, in particular to a polysiloxane elastomer and a preparation method and application thereof. Amino or hydroxyl end capped polydimethylsiloxane, diisocyanate, phenol compounds and a cross-linking agent are dissolved into an organic solvent, a proper amount of catalyst is added, after the reaction is finished, a prepolymer is poured intoa polytetrafluoroethylene mold, heating and solidification are performed, and after the solvent is removed, the novel polysiloxane elastomer is obtained. The polysiloxane elastomer is good in mechanical strength, has the good thermoplasticity, can be reprocessed, has the self-repairing function, and is applied to the fields of flexible electronics, 3D printing, biomedicine and the like.